This weekend belongs to time travel. We're finally seeing the long-awaited release of Looper, the Terminator-inspired gangster movie. And Steven Moffat is writing what I'm guessing will be another timey-wimey episode of Doctor Who. So now's a great moment to think about time travel, and what makes it especially cool.

To a lot of people, time travel stories are cool when they're clever — when all the pieces fit together at the end with a delightful "click." To me, though, time travel stories are cool when they're messy. Because life is messy, and stories in general are cooler when they're rough around the edges.

I've been thinking about how to say this for a long time now — I love time travel stories, but I don't love the kind of time travel stories where everything falls into place and you realize that the rubber duckie at the beginning of the story was actually put there by the guy at the end of the story. It's easy to be superficially clever with that kind of story, and to make the audience feel clever — but oftentimes, that sort of storytelling is not clever at all, it's just a mechanical challenge to put the pieces in the right place.

One of the all-time classic time travel stories is Robert A. Heinlein's "By His Bootstraps," in which everything is a closed loop. The main character — spoiler alert — turns out to be almost all the people he meets, and the whole thing is just this guy going through the motions of acting out a series of fixed events that lead to him becoming the ruler in the future. This is pretty much the classic "everything fits together" story, and it's the one that everybody else is imitating, consciously or unconsciously, when they do this sort of thing.

I always sort of feel as though Heinlein did it first and best, and there's no point in copying that particular story — plus it's the same sort of "aha" cleverness that you get from a story in which a man and a woman wind up on a deserted planet, and then you learn their names are Adam and Eve. Probably whoever came up with that idea first was also being super clever and original, too.

Then there's the variation on that type of story — where it appears as though you can change history, but at the end we still learn that it was all a closed loop. This happens at the end of David Gerrold's otherwise-fantastic novel The Man Who Folded Himself, where Gerrold feels the need to tie everything off with a bow by having the main character give himself the time machine. Likewise, Moffat's best-known "timey wimey" story, "Blink," ends with Sally Sparrow giving the Doctor a detailed set of instructions, so that it turns out the Doctor was just Sally's puppet throughout the entire story and his apparent ingenuity was just following a detailed script.

Your mileage probably does vary somewhat, but I often find these sorts of "tying everything off with a bow" endings actually cheapen the stories they follow.

Four types of time travel

So to be clear, there are a few different theories as to how time travel could work:

1) You can travel back but you can't change anything. If you try to kill Hitler, the gun won't go off. If you try to make even a small change in established history, you'll fail. This version of time travel always seems dangerously close to magic, like the notion that the physical laws of the universe would fail to operate, to prevent you from strangling Julius Caesar. It's also hard to dramatize time travel in which literally no effect is possible.

2) You can travel back, but you always did. In other words, you're predestined to travel back in time, at which point nobody has any agency and the story becomes just a set of pre-ordained events playing themselves out. (This is sort of similar to the Heinlein story, although there it's not clear if the main character can choose to deviate and just doesn't.) A lot of people seem to love this version of time travel stories — either because they feel it's more plausible, or because they feel like it's more clever. Lost notably played with this notion in its penultimate season, where Jack and the others were stuck in the 1970s and (apparently) already a part of established events.

3) You can change the past, and you'll instantly feel the alteration. AKA the Back to the Future rule. The moment Marty McFly inadvertently prevents his parents from getting together, he starts to fade from existence — and unless he ensures their coitus with a display of electric guitar bravado, he'll cease to have existed. We don't see this version of time travel often enough, which is too bad.

4) You can change the past, but you'll just create a brand new timeline. This mostly seems to be how Doctor Who plays it, despite the notion of "fixed points" that you can't change. Star Trek has also toyed with this notion — although Trek has done every possible theory of time travel multiple times. In this version, the time traveler becomes, in effect, a visitor from the "original" timeline, and the only person who can remember the pre-alteration version of history.

Star Trek has played with crazy time-travel shenanigans more than any other franchise - yes, even…
Read more Read more

All four versions of time travel cited above can be done well, or they can be done badly. But I'd argue the third and fourth versions allow for more agency on the part of characters and messier storytelling. It's like if someone offered you the choice between two stories: One in which everything is slotted together gracefully and characters behave in a predictable fashion to make the plot mechanics work — or one in which everything is messy and exciting and characters make tough choices and sacrifices. Which would you prefer? Exactly.

Good stories are about the choices people make, and the consequences those choices have. Bad stories are about people being moved by the plot.

So let's talk about time travel and plausibility. Some people would argue that a version of time travel where you can't change the past is more "realistic." As if there's anything realistic about time travel to begin with. Most physicists seem to believe that time travel is impossible, not least because of the insane energy needs. Other physicists seem to believe the whole concept of "grandfather paradox" shenanigans precludes time travel being achievable. In any case, we're talking about a fantasy technology, no more based on real science than dragons and unicorns.

And there's the fact that "travel" usually implies being able to have an effect on the places you're traveling to. Otherwise, you're not traveling — you're just observing. There's plenty of scope for a good story about people who visit a hologram of the past, or observe the past via a time television or whatever. But if you actually go to the past, I always feel like it should be like going to Italy — you should be able to have ill-advised sex in the back of a Milan disco or throw a bottle at Silvio Berlusconi. Because travelers leave a mark on the places they visit.

Who is John Connor's father?

In The Terminator, Skynet is losing the war against the human resistance — so it decides to send a killer robot disguised as an Austrian bodybuilder back in time, to kill the mother of the resistance leader before she can give birth. The robot fails, and in fact the freedom fighter who goes back in time to defeat the robot winds up becoming the father of the resistance leader. Loop closed, man! (Imagine that last bit said in a Bill Paxton voice.)

So it would seem that the Terminator universe follows schema #2 for time travel — you can go back, but you always went back, and nothing will have changed as a result of your travel. Except that, in order to justify further Terminator outings, the rules had to change somewhat. For one thing, Skynet wouldn't bother to keep sending robots back if all it was doing was getting resistance fighters laid. For another, the possibility of changing history — including preventing Skynet's creation — is what raises the stakes in Terminator 2. By the time you get Terminator 3, the date of Judgment Day has changed, and it's clear new timelines are being created every time someone goes back.

Terminator: The Sarah Connor Chronicles plays with this notion further, implying that the future is a moving target — the future that Derek Reese came from is not the same one that Jesse Flores came from. They remember some key events from the future very differently, and John Connor is a very different person in Jesse's future than in Derek's.

So is Kyle Reese the original father of John Connor? Or was there a timeline in which nobody traveled back in time, and someone else hooked up with Sarah Connor? We asked Sarah Connor Chronicles creator Josh Friedman a few years ago, and he said it was at least possible there was a "pre-Kyle Johnfather" — but then you have a radically different timeline in which Sarah Connor doesn't train her son to be the resistance leader, he just figures it out on his own.

Are you confused by all the alternate timelines in the Terminator franchise? So are we. That's …
Read more Read more

In any case, the Terminator series is Exhibit A for why messy time travel opens up more possibilities than "neat" time travel. The story of John Connor sending his own father back in time to become his father is a cute idea, but it doesn't open up a lot of possibilities beyond that one notion. It's a curio. It's a fancy clockwork sculpture rather than a wild adventure.

And then there's the trope of "ensuring your own past," which is arguably why John Connor feels the need to send Kyle Reese, rather than Jesse Flores or whoever, on that particular mission. It's also a major part of "By His Bootstraps," and it's my least favorite time travel trope. In real life, nobody ever needs to ensure his or her own past. Nobody worries that unless they do this or that, they won't have been born. You know why? Because by definition, the past ensures itself. The past is fixed unless someone changes it — and if you're in a universe where the past cannot be changed, that's twice as much reason not to worry about it. The past is fine.

If someone comes up to you and shows you proof that you're destined to travel back in time to the Middle Ages — your face in a tapestry, or whatever — just shrug and get on with your day. If you're actually destined to go back in time, then nothing you could possibly do will prevent that from happening. By the same token, you don't need to take any action to make that happen — it's already happened, right? The notion that you have to try to do something that you're destined to do has always seemed like the cheapest of plot devices — it's either destiny, or it's not.

And that brings me to the crux of why predestination of all types, including in time travel stories, is less interesting than an unholy mess. It's interesting to watch someone attempt to thwart their destiny and fail — as the story of Oedipus, among others, proves. It's far less interesting to watch people attempt to fulfill a preordained set of events.

In a nutshell: The best time travel stories are adventures. Adventures are messy and unpredictable. Therefore, the best time travel stories are untidy, rather than obsessed with providing the cheap "Aha! That's how it all fits together" moment. Life is a glorious, crazy mess in general — why should time machines make it any different?